KR100675717B1 - Conformable Multilayer Films - Google Patents

Abstract

A compliant multilayer film is provided that alternately has a rigid polymeric material layer and a flexible polymeric material layer.

Compliant Multilayer Film, Rigid Polymer, Flexible Polymer

Description

Conformable Multilayer Films

The present invention relates to a conformable film, and more particularly to a multilayer film having alternating rigid polymeric material layers and flexible polymeric material layers.

There is a need for a compliant non-yielding film that can be bonded to uneven and / or irregular surfaces with many new properties that existing products do not have.

Polyvinyl chloride (PVC) films and tapes are commonly used for a wide variety of applications. One widespread use is for applications in automotive paint masking. PVC has many properties that are beneficial for this application. For example, PVC films are known to be compliant to a variety of topography present outside of automobiles.

However, one drawback of PVC films is the use of plasticizers in PVC films. Typically, plasticizers are needed for PVC films to make the PVC film more flexible, to lower the glass transition temperature of the film, and to make the film more compliant. However, the plasticizer can migrate to the substrate to which the PVC film is attached, leaving a residue or "ghosting" when the film is removed. Ghost cannot be removed by wiping with solvent. Thus, when PVC film is used as tape backing in automobile paint masking tape, it may adversely affect the appearance of the automobile. In addition, such plasticizers can degrade adjacent adhesive layers, reducing tape adhesion to automobiles.

Multilayer films are already disclosed. For example, structures having alternating layers of up to several thousand polymers with different refractive indices are known to have mirror-like properties. Also, cutable or poorly perforated films were made using alternating rigid and soft polymer layers as described in US Pat. Nos. 4,908,278 and 5,427,842 (Bland et al.). Pressure-sensitive adhesive tapes having a multilayer film as a backing on which a pressure-sensitive adhesive is coated are also known.

Although such a multi-layer structure can achieve various properties, there is still a need for a compliant non-yielding film product that replaces poly (vinyl chloride) films.

Summary of the Invention

It is desirable to have alternative compositions for use in tape backings and films. In particular, it is desirable to have alternative compositions for use in automotive paint masking tapes, where stress relief and strain recovery properties are further desired and further minimization of ghost formation is desired.

For applications in graphic film and paint masking, the film has low strain recovery properties and good enough to adhere to the substrate surface without delamination or peeling off of the irregular substrate surface (without "popping up"). It is desirable to have a compliant non-yield film that is easy to paste with stress relaxation properties. In addition, the graphic film must have printability (ie, have a receiving surface for printing and / or graphics) and exhibit good weather resistance for outdoor applications. Drawbacks of PVC and flexible polyolefin films are that they have poor stress relaxation and strain recovery properties and / or ghost formation properties.

The present invention provides an integrated multilayer film having alternating layers of rigid polymeric material and layers of flexible polymeric material. Preferably, the thickness of the multilayer film of the present invention is about 250 micrometers (μm) or less. In one embodiment, the multilayer film has a structure in which different layers of rigid material or different layers of flexible material are present alternately.

In all structures in which the rigid material layer and the flexible material layer are present alternately, each rigid layer may comprise a different material or combination of materials, but typically they comprise the same material or combination of materials. Likewise, each flexible layer may comprise a different material or combination of materials but typically they comprise the same material or combination of materials.

The multilayer film of the invention preferably has a structure in which at least 10, more preferably at least 13, and even more preferably at least 29 substantially contact organic polymer material layers are integrated, but for certain materials 5 It is also possible to have as few layers as there are two or two layers. In some embodiments, there are three or more layers of the same rigid material and often three or more layers of the same flexible material.

The two outermost layers of the multilayer film of the present invention may comprise one or more rigid materials, and the materials of each of the two outermost layers may be the same or different. Alternatively, the two outermost layers can include one or more flexible materials, and the materials of each of the two outermost layers can be the same or different. In addition, the films of the present invention include embodiments in which only one of the outermost layers comprises a rigid material.

In addition, the multilayer film of the present invention may be oriented in one or two directions, if necessary. In addition, the film can be annealed by passing it over a hot roll or through an oven or by heating with an infrared heater. In some embodiments of the invention, the multilayer film may include a layer of flexible material, a layer of rigid material, and a connection layer therebetween.

The present invention also provides a method for producing a multilayer film. The method incorporates a structure incorporating two or more, preferably five or more substantially contacting, organic polymer material layers that alternately comprise a rigid organic polymer material layer and a flexible organic polymer material layer by melt processing the organic polymer material. Forming. Preferably, all the layers are melted at substantially the same time, more preferably all the layers are coextruded at substantially the same time.

In another aspect, the present invention provides a multilayer film having an integrated structure having a total thickness of about 250 μm or less including alternating rigid material containing layers and flexible material containing layers.

In another aspect, the present invention provides a multilayer film having alternating rigid and flexible material layers and further having a pressure sensitive adhesive layer.

In another aspect, the present invention provides a multilayer film having a layer of material, such as a thermoplastic layer or a primer layer, to alter the rigid material layer and the flexible material layer and to improve the ink acceptability of the surface.

Another aspect of the present invention is an organic polymer material of two or more, preferably five or more substantially contacting, alternatively comprising a layer comprising a rigid material and a layer comprising a flexible material by melt processing the organic polymer material. Provided is a method of making a multilayer film comprising forming an integrated structure of layers.

As used herein, the following terms have the following definitions:

A "rigid material" has a Young's modulus greater than about 207 MPa (30,000 psi), more preferably greater than about 345 MPa (50,000 psi), even more preferably greater than about 517 MPa (75,000 psi). Thermoplastic polymers and polymer blends.

“Flexible material” is a thermoplastic polymer having a Young's modulus of less than about 172.4 MPa (25,000 psi), more preferably less than about 68.9 MPa (10,000 psi), most preferably about 0.69 to 68.9 MPa (100 to 10,000 psi); Polymer blends.

 The term "integrated" means that the layers are not separated or delaminated, such as a pressure-sensitive adhesive tape in roll form.

The term "melt viscosity" means the viscosity of the molten material at the processing temperature and shear rate used.

The term "compatibility" means that the film is capable of adapting to bends, depressions or protrusions on the substrate surface such that the film is curved or protrusions on the substrate surface, preferably with minimal necking, without breakage or deposition of the film. It can be stretched along a circumference or pressed down into a depression.

<Detailed Description of Preferred Embodiments>

The present invention relates to multilayer articles in the form of film of organic polymer material (e.g. single or double-sided pressure-sensitive adhesive tape or sheet, backing of tape or sheet, in which a film layer comprising rigid material and a layer comprising flexible material are present alternately. Pressure-sensitive adhesive film). In another preferred embodiment, different layers of rigid material are present alternately (eg, two different layers of rigid material are alternately present). The two outermost layers of the film may comprise a rigid material or a flexible material, or one of the outermost layers may include a rigid material and the other may include a flexible material. Each layer of this structure is continuous and has a substantially in contact with adjacent layers. Preferably, each layer is substantially uniform in thickness. In any structure, multiple layers are "integrated" into a single multilayer film so that the layers are not easily separated.

Multilayer products have a Young's modulus of about 10,000 to 150,000 psi (69 to 1034 MPa) at use temperature, greater than 100% elongation, and less than 55% strain recovery over 24 hours. to be. The term service temperature refers to the temperature at which a film is exposed after pasting onto a substrate. In most cases, the temperature of use will be room temperature, but the film may be exposed to temperatures that are considerably higher or lower than room temperature, such as when the film is attached to a substrate outdoors or to another surface exposed to outdoor conditions. Preferably, the multilayer article has a residual stress of less than 40%.

In addition, the multilayer article preferably has a minimum necking, preferably 25% or less, more preferably 5% or less, when tested according to AS melt stream D 882-95A and the necking test described herein. Necking refers to the tendency of a film to plastically deform under deformation and irreversibly yield. When the film is used as a tape backing, the necking may cause irregular tape lines during gluing.

The Young's modulus of the multilayer film can be conveniently changed by appropriate selection of the flexible material and the rigid material and the selection of the relative ratio of the rigid material and the flexible material (weight percent of the rigid layer and the flexible layer to the film weight). . In order to maximize compliance of the multilayer film, the Young's modulus of the film is preferably in the range of about 68.9 to 344.7 MPa (10,000 to 50,000 psi) for the ˜76-102 μm (˜3-4 mil) film. It will be appreciated that the preferred Young's modulus is affected by the overall thickness of the multilayer film and the relative thickness and number of stiffness and flexible layers. For example, compliance of multilayer films can be maintained in relatively thinner films (1-3 mil thickness range) when using materials with relatively higher Young's modulus. It is desirable that the Young's modulus of the film be about 344.7 to 1034.2 MPa (50,000 to 150,000 psi) in order to maximize the relaxation behavior, deformation recovery and handling (especially when using large sheets) of the film.

Rigid materials used in the present invention include amorphous and semicrystalline thermoplastic homopolymers and copolymers (and mixtures and blends thereof). Useful amorphous polymers generally have a glass transition temperature (T _g ) higher than 50 ° C. (preferably higher than 70 ° C.), and thus the Young's modulus of the rigid layer is greater than about 207 MPa (30,000 psi). In addition, they typically have an elongation of less than 100%.

Examples of useful rigid materials are methyl methacrylate, styrene, alkyl styrenes substituted in the ring, such as α-methyl styrene, acrylonitrile and methacrylonitrile, copolymers of ethylene and vinyl alcohol (e.g. EVOH), Polyesters, polyamides, polyurethanes and polycarbonates. They generally have a melt flow index of 5 or less and are amorphous colorless materials. However, these should not be regarded as limiting features, since rigid materials with crystalline or higher melt flow indices may be used (in fact, such materials may be used when the rigid materials constitute the outer layer). Is required). Preferred rigid material is EVOH.

In addition, small amounts of other materials may be added to the rigid polymer, provided that the mixture satisfies this measure. These additional materials may include flexible polymers, polymer additives such as plasticizers, antioxidants, colorants, flame retardants, UV stabilizers, heat stabilizers, and processing aids such as extrusion aids and lubricants. It is also possible to use materials which are not normally considered rigid, for example flexible polymers, with filler added to increase the modulus of elasticity.

The amount of rigid material used in the film depends on the specific properties required for the multilayer film. However, it has been found that when the materials are coextruded into the multilayer film, the amount of rigid material relative to the weight of the multilayer film is preferably 5 to 80% by weight (preferably 45 to 70% by weight).

Flexible materials useful in the present invention are thermoplastic homopolymers or copolymers or mixtures and blends thereof. The flexible material has a Young's modulus of less than 25,000 psi (172 MPa). Typically, the flexible polymer is a polyolefin based semicrystalline thermoplastic. In addition, small amounts of other materials may be added to the flexible polymer, which presupposes that the mixture satisfies this measure. These additional materials may include rigid polymers, polymer additives such as plasticizers, antioxidants, colorants, flame retardants, UV stabilizers, heat stabilizers, and processing aids such as extrusion aids and lubricants.

Useful flexible materials have elongation of at least 100% at strains of 600% per minute when tensile tested at 25 ° C. Flexible materials are prepared to have a minimum necking as defined in the test procedure below. Yield is the point at which a material film undergoes significant plastic deformation upon further deformation application. Thus, yield is evident at the initial point where strain increase occurs without stress increase in the stress-strain curve.

Many materials are useful as flexible materials. Examples of such materials include homopolymers and copolymers of ethylene, propylene, butene and blends thereof, including copolymers of ethylene with vinyl acetate, acrylic acid, methyl methylacrylate, methacrylic acid, hexene and octene; Polyethylene or polypropylene grafted with maleic anhydride; Polyacrylates; Polyamides, polyester resins and polyurethanes. As the flexible material, low modulus, flexible and preferably non-necked polyolefins such as polyethylene containing 1-octene units or polypropylene having a high level of atactic content are often used. These flexible polyolefins can be blended with polyethylene or isotactic or syndiotactic polypropylene. Preferred flexible materials include homopolymers and copolymers of propylene and blends of polypropylene grafted with maleic anhydride.

(MACROMELT

) 폴리아미드(Henkel Inc.로부터 입수가능함), 그릴론

(GRILON

) 폴리아미드(EMS American Grilon Inc로부터 입수가능함), 바이텔(VITEL) 폴리에스테르(Bostik USA로부터 입수가능함), 하이트렐

(HYTREL

) 폴리에스테르(DuPont으로부터 입수가능함), 모르탄

(MORTHANE

) 폴리우레탄(Morton International로부터 입수가능함), 에스탄

(ESTANE

) 폴리우레탄 (B.F. Goodrich로부터 입수가능함), 크라톤

(KRATON

) 스티렌/이소프렌 또는 스티렌/부타디엔 코폴리머(및 대응하는 수소첨가된 코폴리머) (Shell Chemical Products Inc.로부터 입수가능함), 폴리에틸렌 코폴리머 및 폴리프로필렌 코폴리머, 폴리에스테르 등이 포함된다.The flexible material may also include non-olefin polymers such as flexible polyamides, flexible polyester resins or flexible polyurethanes. Specific examples of these polymers and copolymers include macromelt

(MACROMELT

) Polyamide (available from Henkel Inc.), grillon

(GRILON

) Polyamide (available from EMS American Grilon Inc), VITEL polyester (available from Bostik USA), Hytrel

(HYTREL

) Polyester (available from DuPont), Mortan

(MORTHANE

) Polyurethane (available from Morton International), Estan

(ESTANE

) Polyurethane (available from BF Goodrich), Kraton

(KRATON

) Styrene / isoprene or styrene / butadiene copolymers (and corresponding hydrogenated copolymers) (available from Shell Chemical Products Inc.), polyethylene copolymers and polypropylene copolymers, polyesters and the like.

In general, 20 to 95% by weight of flexible materials have been found useful. More preferably, the film contains about 30 to 55 percent by weight of flexible material when extruded into a multilayer film. The amount of flexible material used in the multilayer film depends, of course, on the particular properties required for the final film and the choice of particular flexible material and particular rigid material. For example, if the rigid material is fragile, such as polymethyl methacrylate, the resulting multilayer film tends to tear when the level of rigid material is high, thus in this case a relatively high level (more than 50%) of flexible Sexual substances are preferred. In contrast, when the rigid material is softer, such as ethylene vinyl alcohol (EVOH), relatively larger amounts and a relatively wider range of compositions are useful.

The materials of the rigid layer (A) and the flexible layer (B) can be modified with one or more processing aids, such as plasticizers, to modify properties such as Young's modulus. Useful plasticizers used with polymeric materials are preferably miscible at the molecular level, ie they can be dispersed or dissolved in thermoplastics. Examples of plasticizers include, but are not limited to, some phthalates with long aliphatic side chains such as polybutene, paraffin oil, waselin, liquid rubber, and tridecyl phthalate. In use, the processing aid is typically present in an amount from about 5 parts to about 300 parts by weight, preferably about 200 parts by weight, based on 100 parts by weight of the polymeric material. If a plasticizer is used, it is desirable that the plasticizer is not incorporated into the outermost layer of the multilayer film (whether the outer layer is flexible or rigid) to avoid the effects of plasticizer migration.

These multilayer articles (ie multilayer films) are typically produced by melt processing (eg extrusion). In a preferred method, the layers are generally formed simultaneously, merged in the molten state and cooled. That is, preferably, the layers are melt processed at substantially the same time, more preferably the layers are coextruded at substantially the same time. Products formed in this way have an integrated structure and have a wide variety of useful, unique and unexpected characteristics, which provide a wide variety of useful, unique and unexpected applications.

Preferably, the thickness of the film is about 250 μm or less (more preferably 150 μm or less, most preferably about 50 μm or less). Such multilayer articles have a structure of at least two layers, preferably at least 5 layers, more preferably at least 13 layers, even more preferably at least 29 layers. Depending on the materials and additives selected, the layer thickness, and the processing parameters used, for example, the multilayer film will typically have different properties in different number of layers. That is, for two specific materials, the same properties (eg tensile strength, flame retardancy) can have maximum or minimum values at different number of layers when compared to two different materials.

The multilayer film may include an (AB) _n structure (eg, (AB) _n A, (BA) _n B or (AB) _n ) having the A and / or B layers as the outermost layers. In this structure, each A layer is rigid as a result of the incorporation of rigid materials that may be the same or different in each layer, and each B layer is the result of the incorporation of flexible materials that may be the same or different in each layer. It's flexible. In addition, the multilayer film has an (AA ') _n structure (eg, (AA') _n A, (A'A) _n A 'or (AA') _n having an A and / or A 'layer as its outermost layer. May be included). In this structure, each of the A layer and the A 'layer includes different rigid materials. In each of these structures, n is preferably 2 or more, more preferably 5 or more, depending on the material used and the desired application.

Multilayer articles preferably exhibit combined compliance and high stress relaxation and low strain recovery. Flexible materials (often polyolefins or polyolefin blends) are particularly preferred for use in graphic marking applications or paint masking applications because flexible polyolefins are economical and have desirable compliance and non-necking behavior. . However, flexible materials are relatively elastic and exhibit insufficient stress relaxation and high strain recovery. However, by layering the rigid thermoplastic polymer with the flexible material, the elastic properties of the film can be greatly reduced. In addition, by multilayer coextrusion, the thickness of the rigid thermoplastic layer can be reduced to the point where the rigid polymer becomes soft. The film obtained shows a synergistic combination of compliance and high stress relaxation with low strain recovery.

Preferred embodiments alternately comprise one, preferably at least three, layers of the same rigid material and at least one, preferably at least three, layers of the same flexible material. Whether the two outer layers are rigid or flexible, or one of the outer layers is rigid and the other is flexible, the multilayer film can be used, for example, as a backing of a single-sided or double-sided pressure-sensitive adhesive tape. In a preferred embodiment, there are generally up to about 500 layers, more preferably up to about 200 layers, most preferably up to about 100 layers, but using the materials and methods described herein It is expected that structures with more layers can be produced.

The individual layers of the multilayer film of the present invention may have the same or different thicknesses. Preferably, each inner layer has a thickness of about 5 μm or less, more preferably about 1 μm or less. However, each of the two outermost layers may be significantly thicker than either inner layer. Preferably, the thickness of each of the two outermost layers is about 150 μm or less. Typically, each layer, whether inner or outermost, has a thickness of at least about 0.01 μm, depending on the material used for forming the layer and the desired application.

Thus, the multilayer film of the present invention can be used as a film for graphic applications. This is because they have advantageous compliance, show less than 25% necking, have good stress relaxation and strain recovery, and have dimensional stability. It is believed that this desirable property results from the alternating incorporation of the rigid material layer and the flexible material layer. Multilayer films are also useful as tape backings for paint masking applications, in which case it is further preferred that the films exhibit less than 5% necking.

Suitable materials for use in making the films of the present invention are those that can be melt processed, whether they are rigid or flexible. That is, it can be flowable or pumped at the temperature used to melt process the film (eg, from about 50 ° C. to about 300 ° C.), which is a film former. In addition, suitable materials do not degrade or gel very much at the temperatures used during melt processing (eg extrusion or compounding). Preferably, such materials have a melt viscosity of about 10 poises to about 1,000,000 poises measured with a capillary melt rheometer at the processing temperatures and shear rates used during extrusion. Typically, suitable materials have a melt viscosity in this range at temperatures of about 175 ° C. and shear rates of about 100 s ⁻¹ .

In the melt processing of the multilayer film of the present invention, the material of the adjacent layers does not have to be compatible or well matched chemically or physically, especially in terms of melt viscosity, but if so required It may be. That is, materials in adjacent polymer flow streams may have a relative melt viscosity (ie, their viscosity ratio) in the range of about 1: 1 to about 1: 2, but they do not have to have such a closely matched melt viscosity. . Rather, the materials of adjacent polymer flow streams may have a relative melt viscosity of at least about 1: 5 and possibly up to about 1:20. For example, the melt viscosity of the flow stream of polymer B (or A) may be similar to, or at least about five times and even up to about 20 times greater than the melt viscosity of the flow stream of adjacent polymer A (or B).

In melt processing films of rigid and flexible materials, the difference in elastic stresses occurring at the interfaces between different polymer layers is also important. Preferably, this elastic difference is reduced or eliminated in order to reduce or eliminate flow instability that may cause layer collapse. Rotational rheometer over a constant frequency range (0.001 rad / sec <ω <100 rad / sec) at processing temperature, with the viscosity at shear rates below 0.01 s ^-1 and the extent to which the viscosity of the material decreases with shear rate Knowing the elasticity of any material measured by the storage modulus of the phase, one skilled in the art can wisely select the relative thickness, die gap and flow rate of the layer to obtain a film with a continuous homogeneous layer.

Importantly, relatively incompatible materials (ie, those that are typically easily delaminated as in conventional two-layer structures) may be used in the multilayer film of the present invention. They may not be suitable for all structures, but they are suitable for structures with many layers. That is, in general, when the number of layers increases, relatively incompatible materials can be used without delamination.

If desired, the functional layer can be applied to one or both major surfaces of the film of the present invention. For example, an adhesive layer can be applied to at least one of the major surfaces. The adhesive layer can be activated by pressure, heat, solvent or any combination thereof, and can be any type based on poly (α olefin), block copolymers, acrylates, rubber / resins, or silicones. The adhesive may be applied at conventional coating weights (eg, 0.0001 to 0.02 g / cm 2) using all conventional coating means such as a spinning rod die, slot die or gravure roll. Other functional layers can also be used. Thus, for example, an abrasive material (optionally included in the binder), a photosensitive layer or an ink receptive layer can be used. Low-adhesion backsize (LAB), which limits the adhesion of various types of surfaces to the film when wound as a coil or stacked on itself, can also be used as the functional layer. The ink receptive surface comprises a material having an affinity for the binder used in the ink. With the ink receptive layer, the multilayer film of the present invention can be used in graphic applications where images, graphics and / or text are transferred to the film by any conventional means, such as screen printing or thermal transfer techniques. If desired, another functional layer can also be used. They can be used alone or in combination with other functional layers on one or both sides of the film.

In addition, the film may be treated with conventional primer coatings and / or activated by flame or corona discharge and / or by other surface treatments to enhance adhesion of the functional layer to it.

If additional pressure sensitive adhesive layers (psa layers) are used, the pressure sensitive adhesives useful in the present invention may be self-adhesive or may require addition of a tackifier. These materials are natural rubbers with tackifiers, synthetic rubbers with tackifiers, styrene block copolymers with tackifiers, acrylate or methacrylate copolymers with tackifiers, self-adhesives or tackifiers. Poly-α-olefins with added imparting agents, and silicones with added tackifiers, but are not limited thereto. Examples of suitable pressure sensitive adhesives are described, for example, in US Pat. Leir et al. Other examples include those described in Encyclopedia of Polymer Science and Engineering, vol. 13, Wiley-Interscience Publishers, New York, 1988); Encyclopedia of Polymer Science and Technology, vol. 1, Interscience Publishers, New York, 1964; And Handbook of Pressure-Sensitive Adhesives, D. Satas, Editor, 2nd Edition, Von Nostrand Reinhold, New York, 1989.

Other additives such as fillers, pigments, crosslinkers, flame retardants, antioxidants, ultraviolet stabilizers and the like may be added to improve the properties of the rigid (A or A ') layer or the flexible (B) layer. Each of these additives is used in an amount that produces the desired result. Pigments and fillers that modify the cohesive strength and stiffness as well as chemical resistance and gas permeability can be used. For example, clays, hydrated silicas, calcium silicates, silico-aluminates, and fine furnace and thermal blacks increase the cohesive strength and stiffness. Plate pigments and fillers such as mica, graphite and talc are preferred for acid / chemical resistance and low gas permeability. Other fillers may include glass or polymer beads or bubbles, metal particles, fibers, and the like. Typically, pigments and fillers are used in amounts of about 0.1% to about 50% by weight, based on the total weight of the multilayer film. Pigments and fillers that modify the optical properties of the film, such as color, opacity and gloss, can also be used.

Crosslinkers such as benzophenones, benzophenone derivatives, and substituted benzophenones such as acryloyloxybenzophenone can also be added and used to increase the modulus of elasticity of each layer polymer. Such crosslinkers are preferably not thermally activated and are activated by radiation sources such as ultraviolet or electron beam irradiation after film formation. Typically, the crosslinker is used in an amount of about 0.1% to about 5.0% by weight based on the total weight of the multilayer film.

Flame retardants may be added to the structure of the invention to incorporate resistance to spark initiation or flame propagation. Examples include brominated aromatic compounds, for example decabromodiphenyloxide, antimony compounds, such as DE83R (Great Lakes, W. Lafayette, IN), eg antimony trioxide or antimony pentoxide, and aluminum 3 Hydrates such as those available under the trade name MICRAL ATH 1500 (Solem Ind., Norcross, GA). Typically, flame retardants are used in amounts of about 1% to about 50% by weight based on the total weight of the multilayer film. Flame retardant polyethylene concentrates are commercially available under the name PE Conc 1 Nat-2P-W (MA Hannah Corp., Elk Grove, IL) containing a flame retardant blend of brominated imide, antimony trioxide and polyethylene polymers. . Flame retardants may be added to the multilayer film of the present invention using the specific flame retardants and amounts described in WO99 / 28128.

In order to prevent severe environmental aging caused by ultraviolet light or heat, ultraviolet stabilizers can be used, including antioxidants and / or hindered amine light stabilizers (HALS). These include, for example, hindered phenols, amines, and sulfur and phosphorus hydroxide degradants. Typically, antioxidants and / or ultraviolet stabilizers are used in amounts of about 0.1% to about 5.0% by weight based on the total weight of the multilayer film.

If necessary, a connection layer, which is typically a hot melt adhesive (ie, sticky when molten), may be used to promote adhesion between each layer. Useful materials for the connecting layer include ethylene / vinyl acetate copolymers (preferably containing at least about 10% by weight of vinyl acetate units), carboxylated ethylene / vinyl acetate copolymers such as CXA 3101 ™ (EI DuPont de Nemors, Inc.), copolymers of ethylene and methyl acrylate, for example POLY-ETH 2205 EMA ™ (Gulf Oil and Chemicals Co.), ethylene / (Meth) acrylic acid copolymers, such as those available under the tradename SURLYN ™ (EI DuPont de Nemours, Inc.), copolymers of polyolefins and polyolefins modified with maleic anhydride, such as Available under the trade name of MODIC ™ (Mitsubishi Chemical Co.), polyolefins containing homogeneously dispersed vinyl polymers, such as VMX ™ (Mitsubishi Chemical Co.) Commercially available, such as FN-70, a ethylene / vinyl acetate based product with a total vinyl acetate content of 50%, and polymethylmethacrylate dispersed with a vinyl acetate content of 23% and a methyl methacrylate content of 23% JN-70 based ethylene / vinyl acetate based product, POLYBOND ™ (acrylic acid believed to be grafted polyolefin) (BP Chemicals Inc., Cleveland, OH), PLEXAR ™ (Believed to be grafted polyolefins) (Quantum Chemicals, Inc., Cincinnati, OH), copolymers of ethylene and acrylic acid, for example Primacor ™ (PRIMACOR ™; Dow Chemical Co., Midland, MI Available under the trade name)), copolymers of ethylene and methacrylic acid, such as those commercially available under the trade name NUCREL ™ (EI DuPont de Nemours, Inc.), And ethylene, Glycidyl methacrylate, terpolymers containing methyl methacrylate, such as those available under the trade name Rotader ™ AX 8900 (Elf Atochem North America, Philadelphia, PA).

The multilayer film of the present invention can be used as a backing or substrate for single or double sided adhesive articles such as tapes. These films are made using extrusion techniques and then coated or coextruded with a low adhesion backsize (LAB) material that limits the adhesion of various types of surfaces to the film when wound as a coil or stacked on itself. Including a wide variety of known adhesive materials (such as all of the pressure-sensitive adhesive materials described herein) and LAB materials (such as polyolefins, acrylates, urethanes, cured silicones, fluorine compounds) as well as solvent coating and extrusion or coextrusion coating techniques A wide variety of known coating techniques can be used.

Multilayer films of the present invention can be made using a variety of equipment well known in the art and many melt processing techniques (such as extrusion techniques). Such equipment and techniques are described, for example, in US Pat. Nos. 3,565,985 (Schrenk et al.), 5,427,842 (Bland et al.), 5,589,122 (Leonard et al.). 5,599,602 (Leonard et al.) And 5,660,922 (Herridge et al.). For example, depending on the desired number of layers and the type of material being extruded, a single manifold or multi-manifold die, a full moon feedblock (e.g., described in US Pat. No. 5,389,324 to Lewis et al.) Alternatively, other types of melt processing equipment can be used.

For example, one technique for making the multilayer film of the present invention may utilize coextrusion techniques such as those described in WO 93/07228 or US Pat. No. 5,660,922 to Herridge et al. In the coextrusion technique, several melt streams are transported to the extrusion die outlet and merged together near the outlet. The extruder is actually a "pump" for delivering the melt stream to the extrusion die. In general, precision extruders are not critical to the process. Many useful extruders are known and include single screw extruders, twin screw extruders, batch-off extruders and the like. Conventional extruders are Davis-Standard Extruders, Inc. (Pocatuck, Connecticut, USA), Black Closone Co. (Black Clawson Co., Fulton, NY), Bustorff Corp. (North Carolina, USA), Farrel Corp. (Connecticut, USA), and Moriyama MFC. Commercially available from various sales agents such as Works, M. T. (Moriyama Mfg. Works, Ltd., Osaka, Japan).

In addition, other pumps may be used to deliver the melt stream to the extrusion die. They include drum loaders, bulk melters, gear pumps, etc., Garco LTI (CA Monterrey), Nordson (CA Westlake), Industrial Machines. Commercially available from a variety of sales agents such as Industrial Machine Manufacturing (Richmond, VA), and Zenith Pumps Division, Parker Hannifin Corp. (North Carolina, USA).

Typically, the feedblock combines the melt streams into a single flow channel. Because of the laminar flow characteristics of the stream, separate layers are maintained for each material. The melt structure then passes through the extrusion die, where the height of the melt stream is reduced and the width is increased to provide a relatively thin and wide structure. Typically, this type of coextrusion is used to produce multilayer film structures having about 5 or more layers.

However, as several coextrusion die systems are known, the use of feedblocks is arbitrary. For example, multi-manifold dies may also be used, such as those commercially available from The Cloeren Company (Orange, Texas, USA). In a multi-manifold die, each material flows from its manifold to the confluence point. In contrast, where a feedblock is used, the materials flow through the single manifold, following the confluence point. When making into a multi-manifold die, the individual material streams in the fluid state are each divided into a predetermined number of smaller or substreams. These smaller streams then merge into layers of a predetermined pattern to form an arrangement of layers of material in the fluid state. In this arrangement the layers are in intimate contact with the adjacent layers. This arrangement generally includes piles of stacked layers, which are later compressed to reduce height. In the multi-manifold die method, the film width remains constant while the stacked piles are compressed, while in the feedblock method the width is expanded. In either case, a relatively thin and wide film is obtained. A layer multiplier can also be used which divides the obtained film into a number of individual subfilms and then stacks them up to increase the number of layers in the final film. Multi-manifold die methods are typically used to make multilayer films having less than about 5 layers.

In making the film, the material may be supplied such that the rigid or flexible material forms the outermost layer. The two outermost layers are often formed of the same material. Preferably, but not necessarily, the layers of materials can be processed at the same temperature. Importantly, although it is generally believed that the melt viscosities of the various layers should be similar, this is not an essential requirement of the method and product of the present invention. Thus, the residence time and processing temperature may need to be adjusted independently (ie for each type of material) depending on the properties of each layer material.

In accordance with the present invention, other fabrication techniques such as lamination, coating or extrusion coating may be used when assembling multilayer films and products from such multilayer films. For example, in lamination, the various layers of the film are joined together at a temperature and / or pressure sufficient to adhere each layer to an adjacent layer (eg, using a heated lamination roller or a heated press).

The continuous forming method involves drawing the pressure sensitive adhesive composition from the film die and then contacting the moving multilayer film. After formation, the pressure sensitive adhesive coating is solidified by quenching using direct methods such as cooling rolls or water baths and indirect methods such as air or gas collisions.

In addition, the film of the present invention can be annealed to minimize or eliminate necking of the film, to reduce asymmetric stresses causing shrinkage in the film and to improve dimensional stability. Usually, the film is coextruded and then passed over a hot roll or through a heated oven or treated with an IR heater. It is preferable to heat-treat the film under the minimum tension to alleviate the asymmetric stress.

If desired, the film of the present invention may be oriented uniaxially (ie substantially in one direction) or biaxially (ie substantially in two directions). This orientation can result in improved strength properties as evidenced by higher modulus and tensile strength. Preferably, the film is prepared by coextrusion of individual polymers to form a multilayer film, followed by stretching and orienting the film at a selected temperature. For example, uniaxial orientation can be achieved by stretching the multilayer film structure in the machine direction at a temperature near the melting point of the film, while biaxial orientation is achieved in the machine and transverse directions at a temperature near the melting point of the film. By stretching. Optionally, thermal curing at a selected temperature may be performed after the orientation step.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope and spirit of the invention. The present invention is presented for illustrative purposes only and should not be construed as limiting the invention.

The invention is further illustrated by the following examples which are not intended to limit the scope of the invention. In the examples, all parts, ratios and percentages are by weight unless otherwise indicated. The following test method was used to characterize the multilayer film.

<Test method>

Stress relaxation test

To determine the tendency of the film to lose stress in a short time, a stress relaxation test was performed. In the first part of the test, a film sample was placed on the jaws of a tensile tester and deformed at a constant rate of 600% per minute until the sample achieved 100% elongation. The jaws were then stopped and the stress was observed for 1 minute under constant strain. The value obtained by dividing the stress at one minute by the original stress at 100% deformation and multiplying by 100 is defined as% residual stress at one minute.

Strain recovery test

To determine the tendency to recover after the film was deformed, a strain recovery test was performed. The film strip was cut and marked in length. The film was then strained to 100% at a strain rate of 600% per minute and held 100% strain for 1 minute. The stress was then removed and the film was allowed to stand for 24 hours, after which the sample length was measured. The difference obtained by dividing the difference obtained by subtracting the length at the time of 100% deformation from the time of 24 hours by the original length before applying the deformation was defined as the strain recovery rate (%) at the time of 24 hours.

Necking test

The necking amount of each sample was determined by examining the stress-strain curve of the sample. The curve was obtained by standard tensile / extension method in an Instron mechanical test frame operating at 30.5 cm / min (12 inches / min). The sample was 12.7 mm (0.5 inches) wide and 50.8 mm (2 inches) gauge length. The thickness of the sample depends on the process conditions and was measured using an Ono Sokki Liner Thickness Gage. The necking percentage was determined by indicating the stress value S1 at the first maximum stress point and the stress value S2 at the next minimum stress point. Necking is defined as 100 x (S1-S2) / S1 and reported as% necking.

Shrink

Unlimited linear heat shrinkage of the plastic film was measured according to AS melt stream D 1204. A film sample of about 25.4 mm in width and about 101.6 mm in length was cut with a die. The longitudinal direction was the same as the direction in which the film was made or the machine direction (MD). A nothch corresponding to the reference point was made at about 75 mm intervals in the longitudinal direction. Each film sample was left unrestricted for 10 minutes in an oven set at one of three temperatures: 163 ° C, 149 ° C, or 135 ° C. The film shrinkage was taken out and measured in MD and transverse direction (CD). MD% contraction is defined as the value obtained by dividing the distance change between the notches by the original distance between the notches and multiplying by 100. CD% shrinkage was defined as the change in width divided by the original width multiplied by 100. Larger values were reported and, unless stated otherwise, MD% contraction.

Substances Used

Substance description

EVOH 105 ethylene vinyl alcohol copolymer, 44 mole% ethylene,

Available from Eval Company of America, Riesle, Illinois, USA.

Rexflex ™ WL101 High Atactic Polypropylene,

(Rexflex ™ WL101) available from Huntsman Polypropylene Corp., Woodbury, NJ.

Vinel ™ 50E555 Maleic Anhydride Graft Polypropylene,

(Bynel ™ 50E555) available from Dupont Packaging and Industrial Polymers, Wilmington, Delaware, USA. Now available as Binel ™ 50E631

Filler A bromide, antimony trioxide and polyethylene polymer

Blend containing 33.75 / 11.25 / 55 weight ratio. PE Conc. From M.A. Hannah, Elk Grove Village, Illinois, USA. Available as 1 Nat-2P-W

Pina ™ 3374 isotactic polypropylene,

(Fina ™ 3374) Available from Fina Oil & Chem, Dallas, Texas

Filler B hindered amine light stabilizer concentrate,

Available as 10407 from Amperset Corporation, Tarrytown, NY, USA

Pigment concentrate of carbon black in filler C 50% by weight polyethylene,

Available as 12085 from Standridge Color Corporation, Social Circle, Georgia, USA

Macromelt ™ 6900 Flexible Polyamide,

(Macromelt ™ 6900) Available from Henkel Adhesives, Elgin, Illinois, USA

Rotader ™ AX8900 Ethylene, Glycidyl Methacrylate, Methyl Methacrylate

Terpolymer containing (Lotader ™ 8900), available from Elf Atochem North America, Philadelphia, PA, USA

Engage ™ 8200 metallocene polymerized olefins containing 24% octane comonomer,                 

(Engage ™ 8200) available from Dow Chemical Co., Midland, Mich.

EVOH F104 ethylene vinyl alcohol copolymer, 32 mole% ethylene,

Available from Eval Company of America in Riesle, Illinois, USA

Copolymers containing Rotader ™ AX8840 ethylene and glycidyl methacrylate,

Available from Elf Atochem North America

HIPS 484 high impact polystyrene,

Available from Dow Plastics, Midland, Mich., USA

VM100 polymethylmethacrylate,

Available from AtoHaas Americas Inc., Philadelphia, PA, USA

Amno nylon 12 polyamide,

Available from Elf Atochem North America

Lexan ™ PC 111N Polycarbonate,

(Lexan ™ PC 111N) available from General Electric Company, Pittsfield, Massachusetts.

PPSC 912 ethylene-propylene copolymer, melt index 65,

Available as ProFax SC 912 from Montel North America, Wilmington, Delaware, USA.

Bitel ™ 4450 aromatic saturated polyester resin,

(Vitel ™ 4450) Bostik Inc. in Middleton, Massachusetts.

Inc.)

LLDPE6806 Linear Low Density Polyethylene

Available from Dow Chemical Co., Midland, Mich., USA

Vinel ™ 41E558 Maleic Anhydride Graft Linear Low Density Polyethylene,

(Bynel ™ 41E558) Available from DuPont Packaging and Indus Trial Polymers, Wilmington, Delaware, USA

Primacor ™ 3440 Poly (ethylene acrylic acid)

(Primacor ™ 3440) Available from Dow Plastics, Midland, Mich.

EVOH G156 ethylene vinyl alcohol copolymer, 48 mole% ethylene,

Available from Eval Company of America in Riesle, Illinois, USA

<Example 1-10, Comparative Example 1-4>

Examples 1-10 illustrate the effect of the number of layers in a multilayer film having A (BA) _n BA structure.

In Example 1, a rigid layer was prepared from EVOH E105 and operated with a Killion single screw extruder (KILLION Model KTS-125, 32 mm, L / D = 24 /) operating at a zone temperature increasing from 182 ° C. to 221 ° C. 1, Killion Extruder Inc. (commercially available from Cedar Grove, NJ) was transported into slot “A” of the feedblock with 91 slots. The feedblock was prepared as described in US Pat. No. 4,908,278 (Brand et al.) And two flow streams alternately fed into 91 slots were joined together into a multilayer flow stream with layers arranged in A (BA) ₄₄ BA. To lose. The temperature of the feedblock and die was set to 232 ° C. The flexible layer was prepared from a mixture of Rexflex ™ WL101 and Vinell ™ 50E555 premixed at a 40:60 weight ratio. The mixture was a twin screw extruder (LEISTRITZ AG Model LSM 34 GL, 34 mm, L / D = 42/1, American Raystres Extruder Corp., Somerville, NJ) operating at zone temperatures increasing from 121 ° C to 232 ° C. (Commercially available from American Leistritz Extruder Corp.) into the "B" slot of the feedblock. The resulting multilayered flow stream was passed through a single orifice film die and collected by drop casting onto a chrome chill roll set at a 24 ° C. temperature. The line speed was 6.7 m / min and the flow rates for each of A and B were such that the weight ratio of the material of the rigid and flexible layers was 30:70 and the total thickness was 102 μm. Part of the structure was then annealed by leaving the multilayer film in an unrestricted state for 5 minutes in an air circulation oven set at 135 ° C.

In Example 2 was prepared as in Example 1, except that the flow rate of the material was adjusted to obtain a weight ratio of 50:50.

In Example 3 was prepared as in Example 1, except that the flow rate of the material was adjusted to obtain a weight ratio of 70:30, the feed block was to be used only 13 slots.

Examples 4 to 6 were prepared as in Example 1, except that only 13 slots could be used for the feed block, and the flow rates of the materials of Examples 4 to 6 were 30:70, 50:50 and 70, respectively. The weight ratio of 30 was adjusted to obtain.

Examples 7 to 10 were prepared as in Example 1 except that the rigid layer was made from EVOH G156 ethylene vinyl alcohol and the number of slots that could be used in the feedblock was 5, 4, 3 and 2, respectively.

Comparative Example 1 was a polyvinyl chloride film about 51 μm thick used for the manufacture of a Controltac ™ 180-10 graphic marking film (available from 3M Company, St. Paul, Minn.).

Comparative Example 2 was a polyvinyl chloride film having a thickness of about 51 μm used for the manufacture of Scotchcal ™ 3650 graphic marking film (available from 3M Company, St. Paul, Minn.).

Comparative Example 3 was a polyurethane film having a thickness of about 51 μm used for the manufacture of a Controltack ™ 190-10 graphic marking film (available from 3M Company, St. Paul, Minn.).                 

Comparative Example 4 was a polyolefin-based film having a thickness of about 100 μm used for the manufacture of Scotchcal ™ 3540C graphic marking film (available from 3M Company, St. Paul, Minn.).

Examples 1-10 and Comparative Examples 1-4 were tested for modulus, residual stress and strain recovery. The test results and the number of layers of the film are shown in Table 1.

As can be seen from the table, the films of the present invention exhibited reduced strain recovery characteristics and equivalent stress relaxation characteristics as compared to those observed in conventional graphic marking films.

Examples 4-7 and Comparative Examples 1-3 were tested for necking. The test results are shown in Table 2.

As can be seen from the table, the annealing of the film substantially reduced the necking when minimal necking was important.

<Examples 11-13>

Examples 11-13 illustrate the effect of fillers on the compliance of multilayer films having A (BA) _n BA structure.

Example 11 was prepared in a similar manner to Example 1 except that the materials were different, and the process conditions were varied so that the number of layers was 13, the weight ratio of the rigid material to the flexible material was 80:20, and the total thickness was about 114 μm. A multilayer film was prepared. Rigid layers were prepared from premixed Filler A and Rexflex ™ WL101 in a weight ratio of 75:25. Rexflex ™ WL101 is normally a flexible material, but has become rigid with filler A addition. The flexible layer was prepared from Remixx ™ WL101 and Pina ™ 3374 premixed in a 75:25 weight ratio. Process temperatures were adjusted to accommodate the melting properties of the various materials.

Example 12 was prepared in the same manner as in Example 1 except that the materials were different, and the process conditions were varied so that the number of layers was 13, the weight ratio of the rigid material to the flexible material was 32:68 and the total thickness was about 87 μm. Phosphorus multilayer film was prepared. The rigid layer was made from EVOH G156. The flexible layer was prepared from a premixed Rexflex ™ WL101 and Vinell ™ 50E555 in a 40:60 weight ratio and then reinforced with Filler B such that the weight ratio of flexible mixture to filler was 100: 15. Process temperatures were adjusted to accommodate the melting properties of the various materials.

Example 13 was prepared in a similar manner as in Example 1 except that the flexible materials were different, the process conditions were varied, the number of layers was 91, the weight ratio of the rigid material to the flexible material was 30:70, and the total thickness was about. A multilayer film of 79 μm was prepared. The flexible layer was prepared from Remixx ™ WL101, Binel ™ 50E555, Filler B and Filler C, premixed at a weight ratio of 40: 48: 8: 4. Process temperatures were adjusted to accommodate the melting properties of the various materials.

Examples 11-13 were tested for modulus, residual stress and strain recovery. The test results and the number of layers of the film are shown in Table 3.                 

As can be seen from the table, fillers can be used without adversely affecting the compliance of the film. Also, in some cases, fillers can have a significant impact on compliance. As indicated above, the rigid layer of Example 11 was a flexible polymer that became rigid due to the presence of filler.

<Examples 14-15>

Examples 14-15 illustrate the effect of the connecting layer on the compliance of the multilayer film having the structure AC (BCAC) _n BCA, where layer C is the connecting layer.

In Example 14 it was prepared in a similar manner as in Example 1 except that a tie layer was added, the tie layer material was fed to the C slot of the multilayer feedblock using a third extruder and the process conditions were varied. The connection layer was made from Macromelt ™ 6900. The tie layer material was transported to the C slot of the feedblock on a Killion single screw extruder (KILLION, 19 mm, L / D = 32/1. Killion Extruders Inc., Cedar Grove, NJ). Process temperatures were adjusted to accommodate the melting properties of the various materials. The process conditions were varied to produce a multilayer film with 65 layers, 50:15:35 weight ratio of rigid material to connecting layer to flexible material, and a total thickness of about 115 μm.

In Example 15, it was prepared in a similar manner as in Example 14 except that the connecting layer and the flexible layer were made from other materials. The linking layer was made from polyethylene with Rotader ™ AX8900 epoxy functional groups. The flexible layer was made from Engage ™ 8200 ethylene / octene copolymer. The total film thickness was about 101 μm.

In Example 16 it was prepared in a similar manner as in Example 14 except that the layers were made from other materials. Rigid, connecting and flexible layers were made from EVOH F104, Rotader ™ AX8900 epoxy containing polyethylene, and Engage ™ 8200 ethylene / octene copolymers, each with 32 mole% ethylene copolymer. The total film thickness was about 109 μm.

Examples 14-16 were tested for modulus, residual stress and strain recovery. The test results and the number of layers of the film are shown in Table 4.

As can be seen from the table, the connecting layer can be used without adversely affecting compliance. Each film was also tested for necking. In Example 14 the necking of the annealed and annealed films was 14% and 2%, respectively. In Example 15 the necking of the annealed and annealed films was 22% and 8%, respectively. The necking of the annealed and annealed films of Example 16 was 19% and 10%, respectively.

<Example 17-28>

Examples 17-28 illustrate the effect of varying variables on the compliance of multilayer films with A (BA) _n BA or B (AB) _n AB structures.

Examples 17-28 were prepared in a similar manner as in Example 1, except that the type, number of layers and weight ratio of rigid to flexible materials were varied in the rigid "A" and flexible "B" layers. . Process temperatures were adjusted to accommodate the melting properties of the various materials. These variables are shown in Table 5 below.                 

Examples 17-28 were tested for modulus, residual stress and strain recovery. The test results and the number of layers of film are shown in Table 6.

1- Film tears before stretching to 100% elongation

As can be seen from the table, satisfactory compliance performance can be obtained in a structure having a wide range of elastic modulus. If the rigid layer material is more fragile, the weight ratio of the rigid component to the flexible component tends to be lower.

<Examples 29-31>

Examples 29-31 illustrate the effect of shrinkage on multilayer films of the present invention. Samples of Examples 29-31 were prepared as in Examples 1, 2, and 24, respectively.

Comparative Example 5 is in accordance with Example 2 of USSN 09/119494 (name of the polymer: polymer blend and tape made therefrom; Kollaja et al.), Except that Pina ™ 3576 is used in place of Escorene ™ 4792E1 ethylene / propylene copolymer. Extruded film prepared from a blend of 60:40 weight ratio Pina ™ 3576 rigid polypropylene and Rexflex ™ WL101 flexible polypropylene.

Comparative Example 6 was plasticized and obtained from Renolit ™ SK-M Signmask Blue (American Renolit Corp., Whitney, NJ). It was a calendered polyvinyl chloride film.

Comparative Example 7 was a plasticized and calendered polyvinyl chloride film available as Lenolit ™ S from American Lenolit Corporation.

All examples were tested for shrinkage. The test results are shown in Table 7 below.

As can be seen from the table, the shrinkage with respect to the temperature used was significantly smaller than that observed in the polyvinyl chloride films of the comparative examples in Examples 29-31. In addition, the film of the present invention had higher dimensional stability (less shrinkage) at 163 ° C. than film (C5) of Comparative Example made from polypropylene blend.

Claims (10)

At least two substantially contacting organic polymer materials that alternately comprise a layer of rigid material having a Young's modulus greater than 50,000 psi (345 MPa) and a layer containing a flexible material having a Young's modulus of less than 25,000 psi (172.4 MPa) A multilayer film having an elongated structure of at least 55%, a Young's modulus of 68.9 to 1034.2 MPa and an elongation of at least 100% at a strain rate of 600% per minute at 25 ° C. The multilayer film of claim 1, wherein the residual stress is 40% or less. delete delete The multilayer film of claim 1 having a necking of 25% or less as measured by AS melt stream D882-95A. The multilayer film of claim 5 having a necking of 5% or less. The multilayer film of claim 1, further comprising a pressure sensitive adhesive layer. The multilayer film of claim 1, further comprising an ink receiving layer. The multilayer film of claim 1, having a Young's modulus of 68.9 to 344.7 MPa (10,000 to 50,000 psi). The multilayer film of claim 1, having a Young's modulus of 344.7 to 1034.2 MPa (50,000 to 150,000 psi).